Heretofore, additives have normally been dispensed into a fuel tank by emptying the contents of a container within a full fuel tank. However, different amounts of fuel are normally used when a fuel tank is filled, because the tank is not normally completely empty. Also, at times, an additive may not be injected when the tank is filled. Thus, an accurate amount of an additive for each gallon of fuel added to a tank is very difficult to achieve.
It is desirable to inject a predetermined amount of additive with fuel into an underground storage tank or a vehicle fuel tank on a regular continuous basis. The term "vehicle" is used in this specification to include mainly trucks and automobiles, but it also includes any machine that has a fuel tank which supplies fuel to an engine. Thus, as used herein, the term vehicle includes boats, airplanes, motorcycles and even motor/generator sets powered by gasoline or fuel oil or irrigation pumps, and the like which do not translate from point to point on the earth. Also, it is desirable that a predetermined amount of the additive be added to the fuel while the fuel is pumped into the fuel tank so that a precise proportion of the additive relative to the fuel be added to the fuel as the fuel is pumped into the fuel tank.